The glycoprotein (Gp) IIb/IIIa is a member of the integrin superfamily of membrane-bound adhesion molecules. Platelet membrane glycoproteins are highly polymorphic and can be recognized as allo-or self-antigens. Incompatibility of epitopes on the various pletelet surface glycoproteins is responsible for the alloimmune thrombocytopenias. The alloantigen most frequently implicated in syndromes of immune mediaated platelet destruction is PLA (or Zw). A case-control study has shown a strong association between the PlA2 allele and unstable coronary syndromes, especially in individuals less than 60 years of age. However, subsequent studies did not confirm this observation. The present study wants to characterize the Gp IIb/IIa genotype and its correlation with fibrinogen binding in healthy North-American subjects. Genotypic analyses of the glycoprotein (Gp) IIb/IIa will be performed on 100 healthy volunteers and the correlation between the GP IIb/IIIa genotype and the extent of fibrinogen binding will be assessed in a subgroup of 30 individuals (15 balanced pairs).